The present invention relates generally to a dispenser for attaching abrasive sheets to a backup pad, and more particularly to a dispenser that conveniently centers on the backup pad an abrasive sheet that is larger than the backup pad.
Abrasives are commonly used to grind, sand, and polish materials such as wood, metal, paint, and plastic. One method of abrading a workpiece is to affix an abrasive sheet to a backup pad, and to rotate the backup pad while urging the abrasive against a workpiece. In many applications, the abrasive sheet and the backup pad are circular, although other configurations are also known. For example, U.S. Pat. No. 4,920,702 (Kloss et al.) discloses a portable grinder having, in one embodiment, a generally triangular backup pad and abrasive sheet that are vibrated rather than rotated.
The abrasive sheet may be affixed to the backup pad in a number of different ways. For example, the use of a pressure sensitive adhesive (see, e.g., U.S. Pat. No. 3,849,949 (Steinhauser et al.)), interengaging fastener members, such as hook portions on the backup pad and loop fabric on the abrasive sheet (see, e.g., U.S. Pat. No. 4,609,581 (Ott)), loop fabric on the backup pad and hooks on the abrasive article (see, e.g., U.S. Pat. No. 5,672,186 (Chesley et al) and U.S. Pat. No. 5,692,949 (Sheffield et al)), intermeshing fasteners (see, e.g., U.S. Pat. No. 4,875,259 (Appeldorn) or U.S. Pat. No. 5,201,101 (Rouser et al.)), and cooperating male and female fastener members, are known in the art.
The backup pad may be configured to be hand held, or may be configured for attachment to a powered abrading apparatus. A typical abrading apparatus includes a rotating output shaft that is powered by an abrading head. These abrading apparatuses, alternatively referred to as grinders herein, may be electrically or pneumatically powered, and typically rotate the backup pad at speeds between 3,000 and 20,000 revolutions per minute. The abrading apparatus may be one of several types. For example, a rotary grinder simply rotates the backup pad and attached abrasive sheet about a fixed axis. A random orbital grinder combines a rotary and orbital motion that results in a random motion of the backup pad with respect to the abrading head.
The diameter of the abrasive sheet is typically larger than the diameter of the backup pad (for example, a 127 mm sheet and a 124 mm pad), to permit abrading near the periphery of the abrasive sheet without damage to the backup pad or to the surface being abraded. It is desirable to position the abrasive sheet relative to the backup pad so that the sheet extends beyond the backup pad around its entire circumference without any of the support surface of the backup pad exposed. It is also desirable to center the abrasive sheet relative to the backup pad so that the amount by which the sheet extends beyond the backup pad is relatively constant along the periphery of the sheet. Typically, the operator of the apparatus applies the abrasive sheet by hand while attempting to center it as well as possible. It is also known to program robotic sanders to attach abrasive sheets centered on the backup pad (see U.S. Pat. No. 5,377,455 (Lanzer)).
Various dispensers for abrasive articles are known, such as those disclosed in U.S. Pat. No. 3,849,949 (Steinhauser et al.) or WIPO International Patent Application Publication No. W096/38264 (King et al.). However, these dispensers do not provide a convenient way to center an abrasive sheet on a backup pad.
It is desirable to provide an abrasive sheet dispenser that simply and effectively centers an abrasive sheet on a backup pad.
One aspect of the present invention provides an abrasive sheet dispenser. The dispenser comprises a holder configured to receive a plurality of abrasive sheets and a spacer. The holder includes a holder inner periphery; a slider guide extending along the holder; and a spacer mounted to the slider guide. The spacer is movable along the slider guide from a first position to a second position and includes an inner surface defining a spacer periphery at a distance from the holder periphery.
In one preferred embodiment of the above dispenser, the holder inner periphery has a first radius of curvature, and the spacer periphery has a second radius of curvature smaller than the first radius of curvature. Preferably, the holder inner periphery is concentric with the spacer periphery.
In another preferred embodiment of the above dispenser, the holder inner periphery forms at least an arc of a first circle having a first radius, and the spacer periphery forms at least an arc of a second circle having a second radius smaller than the first radius. Preferably, the arc of the first circle is concentric with the arc of the second circle. In this embodiment, it is also preferred that the holder inner periphery forms at least a 180 degree arc of a circle. Optionally, the holder inner periphery defines a complete circle. In another preferred embodiment, the spacer periphery defines an arc of no more than 180 degrees.
In another preferred embodiment of the above dispenser, the slider guide comprises an elongate slot extending through the rear portion of the holder.
In another preferred embodiment of the above dispenser, the holder comprises a top and a bottom, and the slider guide extends in the direction between the bottom of the holder and the top of the holder.
In another preferred embodiment of the above dispenser, the holder has a front portion and a rear portion. The slider guide is located in the rear portion, the first position of the holder is within the front portion of the holder, and the second position is beyond the front portion of the holder.
In another preferred embodiment, the above dispenser also includes a base. The holder extends from the base, the slider guide is perpendicular to the base, and the first position of the spacer is closer to the base than the second position of the spacer. In one aspect of this embodiment, the dispenser comprises a unitary molded plastic base and holder.
In another preferred embodiment, the spacer includes a foot extending therefrom. The foot is sized and configured to help hold down the stack of abrasive sheets, and is particularly useful with thin spacers.
Another aspect of the present invention provides a dispenser for circular abrasive sheets. The dispenser comprises a holder configured to receive circular abrasive sheets, the holder including a bottom, a top, front portion and a rear portion, in which the rear portion extends farther from the bottom than the front portion, and in which the bottom of the holder defines at least a 180 degree arc of a first circle having a first radius; a slider guide extending along at least a portion of the rear of the holder in the direction between the top and bottom of the holder; a spacer mounted in the slider guide, the spacer is movable along the slider guide from a first portion within the front portion of the holder to a second position beyond the front portion of the holder, the spacer defining an arc of no more than 180 degrees of a second circle having a second radius smaller than the first radius. In one preferred embodiment, the arcs of the first and second circles are concentric.
In yet another aspect, the present invention provides a method of attaching an abrasive sheet to a support surface of a backup pad, in which the abrasive sheet is larger than the support surface, and the abrasive sheet includes an attachment surface for attachment to the support surface. The method comprises the steps of a) providing the abrasive sheet in a holder of a dispenser such that the attachment surface of the abrasive sheet is exposed, the holder being sized and configured to closely conform to the periphery of the abrasive sheet, the dispenser also includes a spacer within the holder that is sized and configured to closely conform to the periphery of the backup pad; b) contacting the periphery of the backup pad against the spacer to thereby orient the backup pad relative to the abrasive sheet such that the periphery of the abrasive sheet extends beyond the periphery of the support surface of the backup; c) while the backup pad is so oriented, contacting the backup pad against the attachment surface of the abrasive sheet so as to attach the abrasive sheet to the backup pad; and d) removing the backup pad and attached abrasive sheet from the holder. In one preferred embodiment, the backup pad and abrasive sheet are circular, and step b) further includes orienting the support surface of the backup pad such that it is concentric with the abrasive sheet. In another preferred embodiment, step a) further comprises placing a plurality of abrasive sheets into the holder and moving the spacer to contact the top abrasive sheet. This method can include the further step subsequent to step d) of e) moving the spacer towards the plurality of abrasive sheets so as to contact the next adjacent abrasive sheet.